1. Field of the Invention
This invention relates generally to a powertrain that includes a rotary internal combustion engine (ICE) and a planetary gear unit. More particularly the invention relates to such a powertrain for a motor vehicle, in which the engine is driven alternately by a second power source, such as stored pneumatic pressure for starting the engine and accelerating the vehicle from a stopped condition.
2. Description of the Prior Art
Most commercial engines for motor vehicles use internal combustion engines having cylinders and reciprocating pistons, the engines operating on a four stroke Otto cycle or Diesel cycle. The pistons reciprocate within the cylinders and change direction at the end of each piston stroke, twice per power stroke. Each piston must stop at each end of stroke and accelerate again from rest after having lost its momentum, repeating this stopping and starting four times per power stroke. Linear piston displacement is converted to rotation using a crankshaft, which transmits no power when the crank and connecting rod become aligned mutually during each rotation of the crankshaft. Such engines have inherently low operating efficiency.
Rotary engines avoid these limitations and potentially have higher operating efficiency. But they too present problems that affect their cost, power output, engine wear, lubricant sealing, fuel consumption, etc.
To overcome these difficulties, electric hybrid powertrains have been developed, in which an electric motor is located in a torque path between an ICE and a transmission. Power for driving the vehicle is provided by a gasoline or diesel internal combustion engine, or by an electric motor, or by both the engine and motor. But hybrid electric powertrains are expensive to manufacture and assemble.
There is a need for a hybrid powertrain that incorporates the efficiency of a rotary IC engine, eliminates need for a torque converter, and is able to be packaged in a small space in the engine compartment adjacent a transmission.